This invention concerns a loader for sprocket wheels, and also the method to automatically position double-toothing sprocket wheels which use the loader, as set forth in the respective main claims.
The invention is used in machines to produce single-toothing or double-toothing sprocket wheels generated by cutting blades or pinion instruments.
The invention may cooperate with centering devices employed in the case of sprocket wheels with double, straight or bi-helical toothing, wherein the second ring is produced in a subsequent step to the production of the first ring.
The invention is used to carry the pieces to be worked, automatically and in sequence, into correspondence with the operating station of the pinion instrument and subsequently to discharge the completed sprocket wheels from this station, at the same time positioning a new piece to be worked.
The state of the art covers positioning and centering assemblies employed in the production of sprocket wheels; such assemblies substantially comprise a supporting base cooperating with a shaft for the axial positioning and clamping of the piece, and are associated with a pinion instrument acting peripherally to the piece to form teeth thereon.
The unrefined piece is arranged on the supporting base on which it is then made to rotate, while the shaft clamps it in position.
While the piece is rotating the pinion instrument works the piece, rotating and moving alternately and in coordination with the rotation of the supporting base.
In order to work the pieces the worker must load the piece each time onto the supporting base at the beginning of the operation and must remove the piece when the work has been concluded.
These loading and unloading operations considerably slow down the production cycle; it must also be considered that a single worker has to look after two or more machines, and therefore the efficiency of these machines is considerably reduced.
In the production of double-toothing sprocket wheels, or sprocket wheels comprising two rings of teeth which are symmetrical to the median transverse plane of the piece, the worker is obliged to further position the piece in the course of his work since the two rings are made in two different steps and normally on two different machines.
When the second ring has to be made, the piece has to be angularly positioned with extreme precision with respect to the pinion instrument in order to obtain the desired, accurate reciprocal positioning between the teeth of the two rings.
This involves a further lengthening of the working times, with a consequent slow down of the production cycle, a reduction in the efficiency of the machines and an increase in production costs.
WO 88/05364 describes a rotary loader for pieces to be machine-worked, which comprises seatings, open towards the outside, wherein the piece is inserted.
These seatings are delimited by clamping elements, for example wedge-shaped, screwed to the body of the loader and which act under pressure on the side of the piece to be worked.
This kind of loader entails long, complex operations to insert the piece and adapt the size of the seating, which require the wedge-shaped elements to be disassembled.
Moreover, the range of sizes and shapes of the pieces which can be worked is very limited, inasmuch as it is not possible to vary by much the size and the shape of the seating, except by using differentiated clamping elements for every size of piece.
Furthermore, in the housing seatings the pieces to be worked are, for a substantial portion, arranged outside the seating, which can cause knocks or damage during the complete rotation of the loader.
The present applicants have designed, tested and embodied this invention to overcome the shortcomings of the state of the art and to achieve further advantages.